Electronics > Beginners
Cheapest way to make up to 99% pure isopropanol
wasyoungonce:
Yeah I use around 10% distilled water added to IPA for PCB wash. It’s just doesn’t dry or wash properly with straight IPA. But I’d rather be adding to than buying diluted
lordvader88:
Whats the white residue leftover on PCBs after I use mine which is from a drug store and probably %70 or so ?
Shock:
--- Quote from: lordvader88 on June 28, 2019, 09:54:38 pm ---Whats the white residue leftover on PCBs after I use mine which is from a drug store and probably %70 or so ?
--- End quote ---
The salt that Beamin added.
Ian.M:
Easy enough to check for. Evaporate a ml or so to dryness on a watch glass, then, if there is significant residue, do a flame test on the residue. Sodium yellow in a flame test is *SO* obvious - you don't need a fancy platinum wire and high purity hydrochloric acid to clean it - a piece of Nichrome wire cleaned in the flame is plenty good enough.
However the white residue on the board is quite likely to be ionic compounds from the flux, and in that case, you'll have next to nothing on the watch glass to test.
Properly preparing pure dry alcohols is not a good 'kitchen sink' chemistry project - without the correct apparatus with well-fitted joints there's too much risk of fire or explosion and a high probability you'll re-contaminate your product, so if you do have salt (or other sodium compounds) in your IPA change suppliers!
Electro Detective:
I sort of gave up on that stuff, due to the sometimes 'mystery residue' milky stain thing, which members here state is salt :-// and the sometimes longish drying times.
My current fav is non residue electronic contact spray cleaner, either directly sprayed on, or into a container for use with Q-tips, brushes etc.
I buy any decent stuff that's apparently 'safe to use on -most- plastics' in bulk or on sale.
It gets the job done and obliterates gunk, oils and flux etc, dries super fast, and no residue afaict
I use it before and after a large intermittent PCB soldering adventure (prep and post clean) and have had no comebacks or issues ever.
I use it sparingly/wisely because it ain't cheap :phew:
but won't be going back to salty watered down suss isohol any time soon :--
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